Portable OpenSSH 7.5p1 with LibreSSL 2.6.1 fails

Hello,

./config for Portable OpenSSH 7.5p1 with LibreSSL 2.6.1 fails on Debian
Linux:
checking OpenSSL header version... not found
configure: error: OpenSSL version header not found.

$ openssl version
LibreSSL 2.6.1

I did it with this options:

./configure --without-openssl-header-check --sysconfdir=/etc/ssh \
--with-ssl-dir=/usr/local --without-pie --without-xauth \
--with-zlib

How can I fix this?

Thank you in advance.

/Heiko